Enhancement of light Naphtha quality using calcite adsorbent from eggshells by adsorptive desulfurization

Abstract

The presence of sulfur in transportation fuels has bad consequences for health and the environment, and there are many techniques used for removing or eliminating sulfur content, especially hydrodesulfurization. Hydrodesulfurization is the classical technique for desulfurization, but it is characterized by working at elevated temperatures and pressures as well as high costs. For this, there are many alternative methods, such as adsorptive, oxidative, extractive, and so on. The adsorptive desulfurization (ADS) is one of the most promising methods for sulfur reduction because of its ability to work under ambient conditions and ADS can significantly enhance the quality of light naphtha by reducing its sulfur content and improving its suitability for downstream processes such as catalyst poisoning and corrosion. The calcite prepared from eggshell was investigated here as an adsorbent for sulfur compounds from light naphtha. The adsorbent was characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The investigation of adsorbent activity was done by batch adsorption, and the chosen studied variables are temperature, adsorbent dosage, and contact time with ranges of 20–40 C°, 1–3 g, and 15–45 min, respectively, which were designed according to the Box–Behnken experimental design and the experiment results were analyzed using Minitab software version 17. The results show that the sulfur-removing efficacy ranged between 45 and 60%, while optimum sulfur removal efficiency is 61% at the following operation conditions: 40 °C, 3 g, and 45 min for temperature, adsorbent dosage, and adsorption time respectively.Adsorption isotherms Langmuir and Freundlich were examined, and the results show the Freundlich isotherm is more suitable to describe the adsorption of these sulfur compounds.